In 1988, the United States produced a larger volume of polymers and plastics than the entire annual production volume of steel, aluminum, and copper combined. Polymers have become the most common material in our daily lives and are critical items of commerce, industry, and technology. Aqueous solutions which flow at a controlled rate under a given shear stress are also required throughout a variety of industrial applications. Simultaneously, there is enormous need for materials that are ductile at room temperature and can be molded into articles of manufacture or complex shapes. This invention will disclose a unique class of materials that are useful in both applications.
The control of viscosity of water is achieved by adding to water agents such as clays, amounts of polar organic compounds such as polyacrylates, or high concentrations of salts. With the appropriate additives, these aqueous solutions can suspend large amounts of a solid phase and form a thermodynamically stable mixture. These aqueous solutions suspend finely divided solids and will flow slowly when exposed to shear stress. Such solutions, free of solids, also flow more uniformly in situations where numerous paths providing different resistances to flow are open to the fluids.
When a solid must be formed, the materials used to control fluid flow are, generally, not considered. This is because the fluid flow agents form brittle or hydroscopic solids that decompose instead of becoming extrudable when heated. Since materials that can be reformed into articles of manufacture just by heating and plastic processing are very desirable, a large class of compounds which exhibit this behavior have been invented.
However, each of the conventional agents for flow control or solid formation has attendant disadvantages. Hence, a need continues to exist for new agents which are capable of suitably thickening water and aqueous solutions or making objects of manufacture with functional strength and resistance properties. Further, most of the polymeric compounds used in flow control or article manufacture are made from expensive, petrochemical-derived, synthetic chemicals rather than cheaper natural compounds like lignite. Compounds which contain large amounts of lignite are desirable, cheap products because of low raw materials cost. Lignite-containing materials also have a two part structure with the lignite and synthetic parts of the compound tending to phase separate or seek different chemical environments. This difference in affinities produces surface activity which allows the production of very novel thickening agents or plastics. Thickening agents, flow control agents, and thermoplastic solids containing large amounts of lignite are desirable materials because of surface activity, chemical properties, and low materials cost.
Further, there are significant disadvantages in the production of two part molecules containing lignite, particular by chain reaction with a free radical active site. Such processes are disclosed in the patents by Huddleston, U.S. Pat. No. 5,028,271 and U.S. Pat. No. 4,938,803, and the patents of Fry, U.S. Pat. No. 4,703,801 and U.S. Pat. No. 4,676,317. These patents use a polymerization run in the presence of an additive to conduct a free radical reaction. A polymerization run in the presence of an additive is an alteration of an existing polymerization method for reacting a given monomer. An example of the existing polymerization method for the monomer is prepared and the reaction is contaminated with an additive which is supposed to become the backbone of a graft copolymer. The polymerization is run and the product is labeled a graft copolymer of the additive. The problems with this approach are several:
1. Contaminating a previously functional polymerization with an additive allows components of the additive or the additive itself to interfere with the polymerization. The result is a reduced or zero yield of polymer. PA1 2. The polymerization being contaminated with an additive was not designed to initiate polymerization upon and create copolymer with, the additive. If any grafting reactions occur with the additive, they occur in the termination reaction of the polymerization, leading to a. lower molecular weights in the product as the result of chain transfer or b. lower yield as a result of loss of an active polymerization site. PA1 3. Since the polymerization method was a known reaction, it initiates and propagates the polymerization of the monomer just as it was originally designed to do. Graft copolymer may be formed only in termination by combination of radicals or by chain transfer attack of the polymerizing chain onto the backbone. Since these two reactions must compete with the ordinary termination reactions of the polymerization method, they are infrequent and will yield little, if any copolymer. They do not allow quantitative grafting of all molecules of the additive. PA1 4. Any limitations of the method chosen as the basis for the polymerization in the presence of additive continue to be limitations of the method. PA1 1. The plant biomass compacts as time passes so that the tubules, capillaries, and cell structure that permeate early lignite decrease in diameter and length. With increasing age since deposition, these structures become smaller and the lignite changes from a porous media to a microporous solid to an impermeable solid with increasing age. PA1 2. The elemental composition of the lignite changes with time. Thus, if the elemental analysis of a gram of dry lignite were written C.sub.v H.sub.w O.sub.x N.sub.y S.sub.z, then when samples of the lignite were assayed after different amounts of time in the ground, the hydrogen to carbon ratio, w/v, would decrease. Further, the amount of oxygen in the sample, x, would decrease as the millions of years passed. Very crudely, the hydrogen-carbon ratio might change quickly from a modern value of almost 2 to somewhere around 1.2. It then would slowly change from 1.2 toward 0.8 and eventually toward 0.6. PA1 3. As the age of the lignite increases, the fraction of carbon in aromatic structures increases. PA1 4. Simultaneously, the number of aromatic rings fused together into small connected clusters increases from 1 ring toward 4 as the age of the lignite increases. The ring clusters are interconnected by cycloalkyl structures that themselves form 6 member rings. PA1 5. The oxygen in the molecules is in the form of hydroxyl and quinone groups.
It is impossible by previous methods to graft lignite if similarly substituted ethenes with a different dipole moment and sharply reduced water solubility are used in place of ionic, acid, amine, or amide monomers in previously disclosed synthesis methods. With ethene monomers with dipole moments below 1.2 or water solubilities of less than 5.0 g of monomer per 100 g of water at 30.degree. C., reactions run according to previously disclosed procedures give zero yield of graft copolymer.
Lignites are a class of materials often used as fuel. The materials are "short" internment, fossil fuels that would eventually; under the actions of time, pressure, microorganisms, water, and geologic process; become hard coals, bituminous or anthracite. Lignites, also called brown coal, thus range from peats, starting with "mature peats" or "immature brown coals", to bituminous coal. The American Society for Testing and Materials has classified coals by heat content with lignites having a moist-basis, heat value below 19.29 MJoules/Kg. This classification is not absolute, however, and other classification procedures, such as those of the International Classification of Hard Coal by Type or the International Classification for Brown Coals for the Peoples Democracies, differ from this specification.
Peat generally has large pores with less than 50 percent carbon in vitrinite, details of initial plant material still recognizable, and free cellulose present in the material. Soft brown lignite generally has reduced pores with more than 50 percent carbon in vitrinite, details of initial plant material still recognizable, and little or no cellulose present in the material. There is often from 35 to 75 weight percent water in the material as mined. At the transition between soft brown lignite and dull brown lignite, the cell cavities are frequently empty.
Dull brown lignite generally has minimal pores, details of initial plant material still recognizable, and no free cellulose present in the material. There is often from 25 to 35 weight percent water in the material as mined. The percent reflectance of vitrinite is often 0.3 or above and the percent carbon in vitrinite is 65 percent or more. The volatile matter in dry, ash-free vitrinite is usually between 49 and 53 weight percent and the heat content is between 16.7 and 23.0 MJoules/Kg. As soft brown lignite becomes dull brown lignite or brown coal, marked gelification and compaction takes place.
Bright brown lignite generally has cell cavities filled with collinite, details of initial plant material still partially recognizable, and no free cellulose present in the material. There is often from 10 to 25 weight percent water in the material as mined. The percent reflectance of vitrinite is often 0.4 or above and the percent carbon in vitrinite is 70 percent or more. The volatile matter in dry, ash-free vitrinite is usually between 45 and 49 weight percent and the heat content is between 23.0 and 29.3 MJoules/Kg. The properties listed change gradually as the bright brown lignite/coal becomes bituminous hard coal.
The above descriptions are based on the use of lignite as a fuel. Chemically, lignite is a naturally occurring, organogel deposit formed in the anaerobic decomposition of plants under acidic conditions. The simplest difference between the plant and lignite is one million years of weathering, compaction, and rotting., Table, 1 lists some lignite deposits by location and the time since the deposit was layed down. Further data on lignite can be found in "Low-Rank Coal Technology: Lignite and Subbituminous" by G. H. Gronhovd, Noyes Data Corp., Park Ridge, N.J., (1982).
TABLE 1 ______________________________________ Location and Age of Some Lignite Deposits. Location Millions of Years Geologic Period in of the Since Deposition Which Deposition Deposit. Occurred. Occurred. ______________________________________ New Zealand One Pleistocene Tasmania One Pleistocene Alaska Two Pliocene Southeastern Europe Two Pliocene Central Germany Twenty Miocene England Fourty Oligocene ______________________________________
In the time listed in Table 1 between when the plant died and when humans discovered the deposit of plant atoms, major changes take place in how those atoms are bound together. A list of these changes is given below.
A structure which contains some of the appropriate functional groups is shown as structure 1. It may be representative of some parts, interconnections, or sections of molecules in lignite. ##STR1##
Structure 1 is only a display of the type of structure for which chemists have seen spectral and chemical, identifiers. It should not be taken as the actual structure of the molecules that make up lignite. As noted above, however, it should reflect the structures that are found in parts of lignite. Further data on the structure and composition of lignite can be found in "Chemistry of Lignite Liquefaction", prepared for the U.S. Energy Research and Development Administration by the University of North Dakota under contract #E(49-18)-2211, National Technical Information Service, (1976).
No broadly functional methods to graft lignite are known. A method has now been developed which allows ethene monomers to be attached to lignite and lignite polymers and thermoplastics to be made. This invention provides a broad spectrum of soluble or extrudable copolymers and methods for making said copolymers.
The objectives of the present invention include: 1. provide new copolymers containing lignite as the backbone component with a side chain or chains formed from a vinyl monomer; and 2. methods for synthesizing lignite copolymers having vinyl monomer side chain or chains.
Accordingly, it is an object of the present invention to provide a series of methods for synthesizing a lignite graft copolymer. It is also an object of the present invention to provide a spectrum of reagents to use in the processes for preparing the lignite graft copolymer. Further, it is also an object of the present invention to provide a method of boosting or enhancing polymer molecular weights during polymerization reactions. Typical monomers that can be used to add a side chain to lignite are those with the general structure: ##STR2## where R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are organic or inorganic functional groups which do not interfere with free radical polymerization. Alternatively, the reaction can be run with the above monomers and some amount of a diethene compound, ##STR3## where R.sub.5, R.sub.6, and R.sub.7 are organic or inorganic functional groups which do not interfere with free radical polymerization. The diethene compound will cause crosslinking of grafted molecules during the polymerization and, at low concentrations, will produce a higher molecular weight copolymer. At high concentration of diethene compound, a crosslinked solid will be produced by the reaction. These monomers are reacted with lignite to create a two part molecule such that the central lignite network has a molecular weight of about 1,000 to 1,500,000; the total number of random units in a grafted side chain is in the range of 1 to 300,000 units; and the total number of sidechains attached to lignite, x, is in the range of 1 to 500; such that the total copolymer molecular weight is in the range of 1,500 to 30,000,000.